The answer to this question is "PERCEPTION". The term refers to the mental capacity that process of sorting out things, interpreting things mentally, analyzing things and conditions, and integrating stimuli from the sense organs and from the brain and later come up in a concrete and the sensible result after mental processing.
I think the answer would be c. because for birds with longer beaks, it was easier to eat seeds off a cactus (for example), and for birds with shorter seeds, it was easier to eat seeds off the ground.
